Oxalate and Citrate

Inclusion Criteria: Stone formers: * Age 18-70 * History of at least one calcium-based kidney stone Non-stone formers (controls): * Age 18-70 * No history of kidney stone * 24-hour urine oxalate within lab normal (\<50mg/day) Exclusion Criteria: * History of primarily uric acid, cysteine, or struvite stones. * History of severe acid-base abnormality, very low (less than 100mg/day) or very high (greater than 1500mg/day) urine citrate. * Any controls or stone-forming participants who cannot stop diuretic medication or alkali supplementation for the course of the study period. * Non-stone formers and stone-formers with extreme levels of urine citrate will be excluded from this small initial study to reduce heterogeneity and remove focus from the extremes of citrate levels.